A novel production process for chlorobenzene

Abstract

The present application belongs to the technical field of chlorobenzene production, and provides a novel production process of chlorobenzene, which comprises the following steps: step 1, tetraethyl silicate is added into an ethanol solution, stirred uniformly at room temperature, deionized water containing an active component is added, concentrated hydrochloric acid is used to adjust the pH value to 3.7-3.9, after stirring for 2-3 h, the temperature is increased to 70-80 DEG C to continue the stirring reaction, after the reaction is completed, vacuum drying is carried out until the weight is constant, after grinding, calcination is carried out, and a solid acid catalyst is obtained; step 2, benzene dried by a molecular sieve and chlorine dried by concentrated sulfuric acid are continuously introduced into a fixed bed reactor provided with the solid acid catalyst to carry out a chlorination reaction, and a chlorination liquid containing chlorobenzene is obtained; step 3, the chlorination liquid containing chlorobenzene obtained in step 1 is sent into a rectifying tower, separated by a heat pump rectification mode, chlorobenzene is separated out, and the separated chlorobenzene is subjected to dehydration treatment, and chlorobenzene is obtained.

Description

Technical Field

[0001] This invention belongs to the field of chlorobenzene production technology, and specifically relates to a novel production process for chlorobenzene. Background Technology

[0002] Chlorobenzene is an important organic chemical raw material, widely used as an intermediate in fine chemicals such as pesticides, pharmaceuticals, dyes, and rubber additives. It is also a high-performance organic solvent. It has extensive applications in pharmaceuticals, pesticides, dyes, fragrances, and polymer materials, and is a key intermediate in the preparation of phenol, nitrochlorobenzene, aniline, DDT, and polyphenylene sulfide. However, with the continuous development of downstream industries, especially the rapid growth in engineering plastics and fungicides, the market demand for high-purity chlorobenzene has been increasing year by year, placing higher demands on the economic efficiency, environmental friendliness, and safety of its production processes.

[0003] Currently, the main industrial method for producing chlorobenzene is still the fluidized bed chlorination process. This process typically uses Lewis acids such as ferric chloride as catalysts, where dry benzene reacts with chlorine gas in a liquid phase under electrophilic substitution conditions in a chlorination tower. The reaction product is washed with water and alkali to remove catalyst residue, and then unreacted benzene and the byproduct dichlorobenzene are separated through initial distillation and rectification processes to finally obtain the chlorobenzene product. However, in the traditional fluidized bed chlorination process, to control the amount of byproducts such as dichlorobenzene generated, the conversion depth of chlorine gas must be strictly controlled, resulting in a single-pass conversion rate of benzene typically only maintained at around 25%. A large amount of unreacted benzene needs to be separated and recycled, which not only increases energy consumption but also reduces equipment utilization.

[0004] Therefore, developing a new chlorobenzene production process that is highly selective, highly flexible, low-corrosion, low-energy-consumption, and environmentally friendly is of great significance for improving the technological level of the chlorobenzene industry and reducing production costs. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a novel production process for chlorobenzene. This process uses a solid acid catalyst to achieve efficient chlorination of benzene, resulting in high single-pass conversion rate, no wastewater discharge, and low energy consumption.

[0006] The objective of this invention can be achieved through the following technical solutions: A novel production process for chlorobenzene includes the following steps: Step 1: Add tetraethyl silicate to an ethanol solution and stir evenly at room temperature. Add deionized water containing the active component and adjust the pH value to 3.7-3.9 with concentrated hydrochloric acid. After stirring for 2-3 hours, raise the temperature to 70-80℃ and continue stirring to react. After the reaction is completed, dry it in a vacuum drying oven at 120℃ until constant weight. Grind and calcine to obtain a solid acid catalyst. Step 2: Benzene dried by molecular sieve and chlorine gas dried by concentrated sulfuric acid are continuously fed into a fixed-bed reactor containing a solid acid catalyst to carry out a chlorination reaction and obtain a chlorinated liquid containing chlorobenzene. Step 3: The chlorinated liquid containing chlorobenzene obtained in Step 1 is fed into a distillation column and separated by heat pump distillation to obtain chlorobenzene. The separated chlorobenzene is then dehydrated to obtain chlorobenzene.

[0007] In some embodiments of the present invention, the ratio of tetraethyl silicate, ethanol solution, active component and deionized water in step 1 is 4.5-5.0 mL: 60 mL: 0.15-0.18 g: 15 mL.

[0008] In some embodiments of the present invention, the active component is one of phosphotungstic acid and silicotungstic acid.

[0009] In some embodiments of the present invention, in step 1, the particles are ground to a particle size of 360 nm to 500 nm.

[0010] In some embodiments of the present invention, in step 2, the water content of benzene is controlled to be ≤ 100 ppm; and the water content of chlorine is controlled to be ≤ 50 ppm.

[0011] In some embodiments of the present invention, the molar ratio of benzene to chlorine in step 2 is 3 to 5:1.

[0012] In some embodiments of the present invention, the reaction temperature in the fixed-bed reactor in step 2 is 80–120°C, the reaction pressure is 0.1–0.5 MPa, and the reaction time is 5–10 h.

[0013] In some embodiments of the present invention, the distillation column in step 3 includes a high-pressure distillation column and an atmospheric distillation column.

[0014] In some embodiments of the present invention, the pressure of the high-pressure distillation column is 0.6 to 0.8 MPa, and the temperature at the top of the column is 110 to 140°C.

[0015] In some embodiments of the present invention, the pressure of the atmospheric distillation column is 0.1 to 0.2 MPa, and the temperature at the top of the column is 70 to 90°C.

[0016] The beneficial effects of this invention are: This invention uses a solid acid catalyst to replace the traditional FeCl3 homogeneous catalyst. The catalyst is insoluble in the reaction system, which allows the conversion rate of benzene to reach more than 95%, significantly reducing the amount of benzene recycled and the energy consumption for separation. At the same time, there is no catalyst residue in the chlorination liquid, eliminating the need for water washing and alkali washing processes, and completely avoiding the generation of phenol-containing wastewater from the source, which is a clean production process.

[0017] This invention also provides a solid acid catalyst prepared by a sol-gel method, using tetraethyl silicate as the silicon source and phosphotungstic acid or silicotungstic acid as the active component, through hydrolysis-condensation under acidic conditions, drying, grinding, and calcination. The obtained solid catalyst has the following characteristics: highly dispersed active components, good accessibility to acid centers, and high catalytic efficiency; its mesoporous pore structure and suitable acid strength are conducive to the formation of the target product chlorobenzene, while effectively inhibiting the formation of byproducts such as dichlorobenzene; simultaneously, chemical bonds are formed between the active component and the support, making it less prone to loss. Furthermore, this catalyst also possesses good regenerability; after deactivation, calcination under an air atmosphere can restore its excellent initial activity.

[0018] This invention provides a novel production process for chlorobenzene. The process is simple, eliminating the need for water washing, alkaline washing, and wastewater treatment. This avoids potential moisture residue and side reactions associated with water washing. The resulting chlorobenzene product has high purity, stable color, and no metal ion residue, making it suitable for a wide range of applications. Furthermore, the process is streamlined, requiring less equipment investment and floor space, and has low operating and maintenance costs, making it suitable for large-scale production. Detailed Implementation

[0019] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] Obviously, the following description is merely some examples or embodiments of this application. Those skilled in the art can apply this application to other similar scenarios without any inventive effort. Furthermore, it is understood that although the effort involved in such development may be complex and lengthy, for those skilled in the art related to the content disclosed in this application, any changes to design, manufacturing, or production based on the technical content disclosed in this application are merely conventional technical means and should not be construed as insufficient disclosure of the content of this application.

[0021] However, there may be instances where unnecessary detailed descriptions are omitted. For example, detailed descriptions of well-known matters or repetitive descriptions of essentially the same structure may be omitted. This is to avoid making the following description unnecessarily lengthy and to facilitate understanding by those skilled in the art. Furthermore, the following description is provided to enable those skilled in the art to fully understand this application and is not intended to limit the subject matter of the claims.

[0022] Example Example 1 This embodiment provides a novel production process for chlorobenzene, including the following steps: Step 1: Add 4.5 mL of tetraethyl silicate to 60 mL of ethanol solution (the volume ratio of anhydrous ethanol to deionized water is 2:3), stir evenly at room temperature, add 15 mL of deionized water containing 0.15 g of phosphotungstic acid, adjust the pH value to 3.7 with concentrated hydrochloric acid, stir for 2 h, then raise the temperature to 70 °C and continue stirring to react. After the reaction is completed, place it in a vacuum drying oven at 120 °C to dry to constant weight, grind to a particle size of 360 nm, and then calcine to obtain a solid acid catalyst. Step 2: Benzene (water content ≤100ppm) dried by molecular sieve and chlorine (water content ≤50ppm) dried by concentrated sulfuric acid are continuously fed into a fixed-bed reactor containing a solid acid catalyst at a molar ratio of 3:1 to carry out the chlorination reaction. The reaction temperature is 80℃, the reaction pressure is 0.2MPa, and the reaction time is 6h to obtain a chlorinated liquid containing chlorobenzene. Step 3: The chlorinated liquid containing chlorobenzene obtained in Step 1 is fed into a high-pressure distillation column and an atmospheric distillation column. The pressure of the high-pressure distillation column is 0.6 MPa and the top temperature is 110°C. The pressure of the atmospheric distillation column is 0.1 MPa and the top temperature is 70°C. Chlorobenzene is separated by heat pump distillation. The separated chlorobenzene is then dehydrated to obtain chlorobenzene.

[0023] Example 2 The only difference from Example 1 is that step 1 is different: Step 1: Add 4.8 mL of tetraethyl silicate to 60 mL of ethanol solution (the volume ratio of anhydrous ethanol to deionized water is 2:3), stir evenly at room temperature, add 15 mL of deionized water containing 0.165 g of phosphotungstic acid, adjust the pH value to 3.7 with concentrated hydrochloric acid, stir for 2 h, then heat to 70 °C and continue stirring to react. After the reaction is completed, place it in a vacuum drying oven at 120 °C to dry to constant weight, grind to a particle size of 460 nm, and then calcine to obtain a solid acid catalyst.

[0024] Example 3 The only difference from Example 1 is that step 1 is different: Step 1: Add 5.0 mL of tetraethyl silicate to 60 mL of ethanol solution (the volume ratio of anhydrous ethanol to deionized water is 2:3), stir evenly at room temperature, add 15 mL of deionized water containing 0.18 g of silicotungstic acid, adjust the pH value to 3.8 with concentrated hydrochloric acid, stir for 3 h, then heat to 80 °C and continue stirring to react. After the reaction is completed, place it in a vacuum drying oven at 120 °C to dry to constant weight, grind to a particle size of 480 nm, and then calcine to obtain a solid acid catalyst.

[0025] Example 4 The only difference from Example 1 is that step 2 is different: Step 2: Benzene (water content ≤100ppm) dried by molecular sieve and chlorine (water content ≤50ppm) dried by concentrated sulfuric acid are continuously fed into a fixed-bed reactor containing a solid acid catalyst at a molar ratio of 5:1 to carry out the chlorination reaction. The reaction temperature is 80℃, the reaction pressure is 0.2MPa, and the reaction time is 6h to obtain a chlorinated liquid containing chlorobenzene.

[0026] Example 5 The only difference from Example 1 is that step 2 is different: Step 2: Benzene (water content ≤100ppm) dried by molecular sieve and chlorine (water content ≤50ppm) dried by concentrated sulfuric acid are continuously fed into a fixed-bed reactor containing a solid acid catalyst at a molar ratio of 3:1 to carry out the chlorination reaction. The reaction temperature is 120℃, the reaction pressure is 0.4MPa, and the reaction time is 8h to obtain a chlorinated liquid containing chlorobenzene.

[0027] Example 6 The only difference from Example 1 is that step 3 is different: Step 3: The chlorinated liquid containing chlorobenzene obtained in Step 1 is fed into a high-pressure distillation column and an atmospheric distillation column. The pressure of the high-pressure distillation column is 0.8 MPa and the top temperature is 130°C. The pressure of the atmospheric distillation column is 0.1 MPa and the top temperature is 70°C. Chlorobenzene is separated by heat pump distillation. The separated chlorobenzene is then dehydrated to obtain chlorobenzene.

[0028] Example 7 The only difference from Example 1 is that step 3 is different: Step 3: The chlorinated liquid containing chlorobenzene obtained in Step 1 is fed into a high-pressure distillation column and an atmospheric distillation column. The pressure of the high-pressure distillation column is 0.6 MPa and the top temperature is 110°C. The pressure of the atmospheric distillation column is 0.2 MPa and the top temperature is 80°C. Chlorobenzene is separated by heat pump distillation. The separated chlorobenzene is then dehydrated to obtain chlorobenzene.

[0029] Comparative Example Comparative Example 1 The only difference from Example 1 is that step 1 is different: Step 1: Add 3.3 mL of tetraethyl silicate to 60 mL of ethanol solution (the volume ratio of anhydrous ethanol to deionized water is 2:3), stir evenly at room temperature, add 15 mL of deionized water containing 0.15 g of phosphotungstic acid, adjust the pH value to 3.7 with concentrated hydrochloric acid, stir for 2 h, then heat to 70 °C and continue stirring to react. After the reaction is completed, place it in a vacuum drying oven at 120 °C to dry to constant weight, grind to a particle size of 360 nm, and then calcine to obtain a solid acid catalyst.

[0030] Comparative Example 2 The only difference from Example 1 is that step 1 is different: Step 1: Add 4.5 mL of tetraethyl silicate to 60 mL of ethanol solution (the volume ratio of anhydrous ethanol to deionized water is 2:3), stir evenly at room temperature, add 15 mL of deionized water containing 0.08 g of phosphotungstic acid, adjust the pH value to 3.7 with concentrated hydrochloric acid, stir for 2 h, then raise the temperature to 70 °C and continue stirring to react. After the reaction is completed, place it in a vacuum drying oven at 120 °C to dry to constant weight, grind to a particle size of 360 nm, and then calcine to obtain a solid acid catalyst.

[0031] Comparative Example 3 The only difference from Example 1 is that step 2 is different: Step 2: Benzene (water content ≤100ppm) dried by molecular sieve and chlorine (water content ≤50ppm) dried by concentrated sulfuric acid are continuously fed into a fixed-bed reactor containing a solid acid catalyst at a molar ratio of 2:1 to carry out the chlorination reaction. The reaction temperature is 80℃, the reaction pressure is 0.2MPa, and the reaction time is 6h to obtain a chlorinated liquid containing chlorobenzene.

[0032] Comparative Example 4 The only difference from Example 1 is that step 2 is different: Step 2: Benzene (water content ≤100ppm) dried by molecular sieve and chlorine (water content ≤50ppm) dried by concentrated sulfuric acid are continuously fed into a fixed-bed reactor containing a solid acid catalyst at a molar ratio of 3:1 to carry out the chlorination reaction. The reaction temperature is 60℃, the reaction pressure is 0.2MPa, and the reaction time is 4h to obtain a chlorinated liquid containing chlorobenzene.

[0033] Comparative Example 5 The only difference from Example 1 is that step 3 is different: Step 3: The chlorinated liquid containing chlorobenzene obtained in Step 1 is fed into a high-pressure distillation column, wherein the pressure of the high-pressure distillation column is 0.6 MPa and the top temperature of the column is 110℃. The chlorobenzene is separated by heat pump distillation. The separated chlorobenzene is then dehydrated to obtain chlorobenzene.

[0034] Comparative Example 6 The only difference from Example 1 is that step 3 is different: Step 3: The chlorinated liquid containing chlorobenzene obtained in Step 1 is fed into a high-pressure distillation column and an atmospheric distillation column. The pressure of the high-pressure distillation column is 0.4 MPa and the top temperature is 100℃, while the pressure of the atmospheric distillation column is 0.1 MPa and the top temperature is 70℃. Chlorobenzene is separated by heat pump distillation. The separated chlorobenzene is then dehydrated to obtain chlorobenzene.

[0035] Comparative Example 7 The only difference from Example 1 is that step 3 is different: Step 3: The chlorinated liquid containing chlorobenzene obtained in Step 1 is fed into a high-pressure distillation column and an atmospheric distillation column. The pressure of the high-pressure distillation column is 0.6 MPa and the top temperature is 110°C. The pressure of the atmospheric distillation column is 0.3 MPa and the top temperature is 100°C. Chlorobenzene is separated by heat pump distillation. The separated chlorobenzene is then dehydrated to obtain chlorobenzene.

[0036] Performance testing The conversion rate, selectivity, and purity of benzene in the novel production processes of chlorobenzene provided in Examples 1 to 7 and Comparative Examples 1 to 7 were tested. The test results are shown in Table 1. Table 1

[0037] As shown in Table 1, the novel chlorobenzene production processes provided in Examples 1-7 all achieve high conversion rates, high selectivity, and high purity chlorobenzene production, indicating that the processes possess good flexibility, stability, and industrial application potential. Combining Comparative Examples 1-2 with Example 1, it can be seen that insufficient support or active components in the solid acid catalyst lead to a decrease in the density of acidic centers, resulting in a decrease in the conversion rate of chlorobenzene. Combining Comparative Example 3 with Example 1, it can be seen that when the material ratio of benzene and chlorine is unbalanced, excessive chlorine leads to deep chlorination, increasing byproducts such as dichlorobenzene, thus reducing the selectivity of chlorobenzene. Combining Comparative Example 4 with Example 1, it can be seen that when the temperature is too low, the reaction rate is slow, and insufficient reaction time also leads to incomplete reaction, reducing the conversion rate of benzene. Combining Comparative Examples 5-7 with Example 1, it can be seen that incomplete reaction separation easily results in residual byproducts and unreacted substances in the product, leading to a decrease in the purity of chlorobenzene. Insufficient or excessively high distillation pressure and temperature also reduce separation efficiency, ultimately leading to a decrease in product purity.

[0038] It should be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. It should be understood that, in the various embodiments of this application, the sequence number of each process does not imply a sequential order of execution; some or all steps may be performed in parallel or sequentially; the execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of this application.

[0039] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this application are available on the market or can be prepared by existing methods.

[0040] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions, and all technical features and optional technical features of this application can be combined to form new technical solutions.

[0041] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A novel production process for chlorobenzene, characterized in that, Includes the following steps: Step 1: Add tetraethyl silicate to an ethanol solution and stir evenly at room temperature. Add deionized water containing the active component and adjust the pH value to 3.7-3.9 with concentrated hydrochloric acid. After stirring for 2-3 hours, raise the temperature to 70-80℃ and continue stirring to react. After the reaction is completed, vacuum dry to constant weight, grind and calcine to obtain a solid acid catalyst. Step 2: Benzene dried by molecular sieve and chlorine gas dried by concentrated sulfuric acid are continuously fed into a fixed-bed reactor containing a solid acid catalyst to carry out a chlorination reaction and obtain a chlorinated liquid containing chlorobenzene. Step 3: The chlorinated liquid containing chlorobenzene obtained in Step 1 is fed into a distillation column and separated by heat pump distillation to obtain chlorobenzene. The separated chlorobenzene is then dehydrated to obtain chlorobenzene.

2. The novel production process for chlorobenzene according to claim 1, characterized in that, In step 1, the ratio of tetraethyl silicate, ethanol solution, active component and deionized water is 4.5-5.0 mL: 60 mL: 0.15-0.18 g: 15 mL.

3. The novel production process for chlorobenzene according to claim 1, characterized in that, The active component is one of phosphotungstic acid and silicotungstic acid.

4. The novel production process for chlorobenzene according to claim 1, characterized in that, In step 1, the particles are ground to a size of 360nm to 500nm.

5. The novel production process for chlorobenzene according to claim 1, characterized in that, In step 2, the water content of benzene is controlled to be ≤ 100 ppm; the water content of chlorine is controlled to be ≤ 50 ppm.

6. The novel production process for chlorobenzene according to claim 1, characterized in that, In step 2, the molar ratio of benzene to chlorine is 3 to 5:

1.

7. The novel production process for chlorobenzene according to claim 1, characterized in that, In step 2, the reaction temperature in the fixed-bed reactor is 80–120℃, the reaction pressure is 0.1–0.5 MPa, and the reaction time is 5–10 h.

8. The novel production process for chlorobenzene according to claim 1, characterized in that, The distillation columns in step 3 include high-pressure distillation columns and atmospheric distillation columns.

9. A novel production process for chlorobenzene according to claim 8, characterized in that, The pressure of the high-pressure distillation column is 0.6–0.8 MPa, and the temperature at the top of the column is 110–140 °C.

10. A novel production process for chlorobenzene according to claim 8, characterized in that, The pressure of the atmospheric distillation column is 0.1–0.2 MPa, and the temperature at the top of the column is 70–90 °C.

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